A CURE for blindness by reversing damage to the retina could be on the horizon - thanks to the humble zebrafish, according to new research.

PUBLISHED: PUBLISHED: 17:01, Thu, Mar 9, 2017

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The eyes of the zebrafish could hold the key to curing blindness, researchers find

Scientists have identified a brain chemical that could hold the key to how the fish regrows damaged retinas, the light sensing tissue at the back of the eye.

Its levels drop when the unique self repair process kicks in - so blocking it could lead to new treatments for AMD (age related macular degeneration), the most common cause of blindness.

There are two forms, dry and wet, and they affect at least half a million people in the UK to some extent. It causes damage to the macula, a small spot near the centre of the retina needed for sharp, central vision.

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Graduate student Mahesh Rao got the idea GABA, best known for its role of calming nervous activity by inhibiting nerve transmission in the brain, might be the trigger for retinal regeneration.

Experiments with zebrafish, an important animal model for studying regeneration, then found high concentrations of GABA in the retina keep the Müller glia inactive. They begin altering and proliferating when GABA concentrations drop.

Prof Patton said: "Last month a paper was published in the journal Cell that reports GABA levels play a central role in the regeneration of pancreas cells.

"We now have three instances where GABA is involved in regeneration - the hippocampus, the pancreas and the retina - so this could be an important, previously unknown role for the neurotransmitter."

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In the UK 44,000 people a year develop dry AMD

They showed this in two ways, by blinding zebrafish and injecting them with drugs that stimulate GABA production and by injecting normal zebrafish with an enzyme that lowers the GABA levels in their eyes.

Zebrafish are easily blinded but due to their robust regenerative ability their eyes recover in just 28 days.

When the biologists injected drugs that kept GABA concentrations in the retinas of newly blinded fish at a high level, they found it suppressed the regeneration process.

After injecting an enzyme that lowers GABA levels in normal fish, they found that the Müller glia began changing and proliferating, the first stage in the regeneration process.

Prof Patton said: "Our theory is a drop in GABA concentration is the trigger for regeneration. It initiates a cascade of events that includes the activation of the Müller glia and the production of various growth factors that stimulate cell growth and proliferation."

The dry form of AMD affects 85 per cent of patients and causes gradual loss of central vision, but does not affect peripheral vision. The Macular Society estimates 44,000 people a year in the UK develop dry AMD.